Damp-proof course (D.P.C.) best practice in building construction: Which statements are correct?

Introduction / Context:
Damp-proof courses (D.P.C.) prevent capillary rise of moisture and lateral moisture ingress through walls and floors. A correct D.P.C. specification is crucial to avoid efflorescence, plaster failure, mold growth, and timber decay. This question reviews fundamental requirements applicable on site.

Given Data / Assumptions:

• D.P.C. is a layer of impervious material installed at strategic levels in walls and floors.
• Materials may include polymer-modified asphaltic membranes, bitumen felt, dense cement mortar with admixtures, or polymer sheets.
• Continuity and proper lapping at intersections are essential.

Concept / Approach:
A D.P.C. must be continuous to be effective; any discontinuity permits moisture bypass. The material must be adequately impervious and durable. Depending on detail, a horizontal D.P.C. (e.g., above plinth) blocks rising damp, while vertical D.P.C. (or tanking) protects abutments, retaining walls, and areas exposed to lateral moisture. Proper interface details at junctions ensure that both orientations work together.

Step-by-Step Solution:
Check (a): continuity is mandatory to prevent moisture bridges → correct.Check (b): only impervious, durable materials can provide long-term damp-proofing → correct.Check (c): both horizontal and vertical applications exist and are often combined (e.g., floor-to-wall) → correct.Therefore, select “All the above”.

Verification / Alternative check:
Site manuals and codes emphasize continuous, well-lapped D.P.C. with compatible materials at junctions; failures typically trace back to discontinuities or unsuitable materials.

Why Other Options Are Wrong:
Limiting to only some statements ignores common, necessary practices such as vertical damp-proofing in splash or retaining conditions.

Common Pitfalls:
Interrupting D.P.C. at door thresholds, poor lapping at corners, or piercing the D.P.C. with fixings without proper sealing.

Final Answer:
All the above.